Antibiotic resistance profile in sediments and bacterial isolates from a human-impacted mangrove from Bahía Magdalena, Mexico.

Antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs) in the environment are considered emerging contaminants. One of the ecosystems that can harbor resistant bacteria and genes is mangroves. This report aims to assess ARB and ARG's presence at two mangrove locations in Bahia Magdalena, Mexico. Bacterial isolates were selected based on their phenotypic profiles of antibiotic resistance. DNA from mangrove sediments and bacterial isolates was tested for int1 and antibiotic resistance genes by final point PCR. From 90 ARB isolates, the phenotypic profile showed resistance to ciprofloxacin (90%), cefotaxime (85.7%), and ampicillin (78.6%), while the beta-lactamase gene (blaCTX-M) was present in 72.9% of the isolates. Antibiotic resistance genes identified in sediments were found even at 30-50 cm depth, but the integron Class gen (int1) was found mainly in shallow samples. Principal component analysis showed a close relationship between the integron gene, vancomycin, and sulfonamides resistance genes. No correlation was found between the phenotypic and genotypic profiles of the bacterial isolates. Also, no differences were observed between the two mangrove ecosystems studied. The impact of anthropogenic activities was equally significant on both sites. The role of mangrove ecosystems in the dispersion of antibiotic resistance needs to be further explored.